Manually operated suspended crane assemblies such as a gantry crane or bridge crane are used in a great variety of industrial and other applications for lifting and moving objects. Suspended crane assemblies can be designed to lift and move any practical weight.
Existing suspended crane assemblies generally include a crane, which is suspended from a trolley that is, in turn, suspended from at least one bridge. The trolley is capable of longitudinal movement along the at least one bridge. The at least one bridge is movably supported (generally in a suspended manner) at either end from a pair of parallel tracks or guides. The tracks or guides are generally mounted to a building ceiling or roof structure. Alternatively, the tracks or guides (hereinafter referred to simply as “guides”) could be supported from a steel superstructure. This is a particularly attractive option in situations where the building ceiling or roof structure concerned is not designed to bear loads.
One problem with existing assemblies occurs when an operator attempts to initiate movement of the bridge in either direction relative to the guides. The effort required to initiate such movement is often considerable, at least in part owing to the fact that movement of the other end of the bridge is initiated. This can cause the bridge to twist relative to the stationary guides, and thereby jam and prevent further movement.
Another problem with existing assemblies is the fact that the guides must be aligned parallel or very close to parallel during installation. If not, the bridge tends to jam in the guides preventing further movement.